For hair dyeing, two-part type permanent hair dyes composed of a first part containing an alkali agent and a second part containing an oxidizing agent have been used popularly. The oxidizing agent of the second part is added in order to impart a bright color tone to the hair by enhancing the hair dyeing effect through the coupling reaction of an oxidation dye intermediate and at the same time accelerating oxidation and decomposition of melanin granules in the hair. The alkali agent of the first part is, on the other hand, incorporated in order to enhance the hair dyeing effect and activate the action of the oxidizing agent to enhance the bleaching effect. For Bleaching or dyeing of the hair into a brighter color tone compared with the original color tone of the hair, sufficient bleaching power is necessary. Hair bleaching power however usually depends on the amounts of alkali and oxidizing agents, so that they must be added in large enough amounts when the hair dye is used for such a purpose.
Conventional hair dyes contain ammonia or organic amines as the alkali agent and hydrogen peroxide as the oxidizing agent. Addition of them in large amounts is however accompanied with the drawback that it is apt to damage the hair or irritate the scalp in proportion to the amount used.